OSCILLATOR

• US 20170104475A1
• Filed: 06/02/2015
• Published: 04/13/2017
• Est. Priority Date: 06/10/2014
• Status: Active Grant

• Current Assignee: Agency For Science Technology and Research (Government of Singapore)
• Original Assignee: Agency For Science Technology and Research (Government of Singapore)
• Inventors: Lam, Yat Hei
• Granted Patent: US 10,256,797 B2
• Time in Patent Office: Days
• CPC Class Codes: H03B 5/24 active element in amplifier being semiconductor device H03B5/26 takes precedence
• CPC Class Codes: H03H 11/0422 using transconductance amplifiers, e.g. gmC filters
• CPC Class Codes: H03K 3/02 Generators characterised by the type of circuit or by the means used for producing pulses H03K3/64 - H03K3/84 take precedence
• CPC Class Codes: H03K 3/0231 Astable circuits H03K3/0315 takes precedence
• CPC Class Codes: H03K 3/0377 Bistables with hysteresis, e.g. Schmitt trigger non-regenerative amplitude discriminators G01R19/165
• CPC Class Codes: H03K 4/502 the capacitor being charged from a constant-current source
• CPC Class Codes: H03L 7/1075 by changing characteristics of the loop filter, e.g. changing the gain, changing the bandwidth H03L7/1072 takes precedence

Abstract

According to embodiments of the present invention, an oscillator is provided. The oscillator includes a switched capacitor circuit arrangement configured to generate a predetermined voltage, a transconductance-capacitor filter configured to receive the predetermined voltage and a reference voltage, and to generate an output filter voltage based on a differential result between the predetermined voltage and the reference voltage, wherein a value of the output filter voltage is variable in response to the differential result, and a period control circuit arrangement configured to receive the output filter voltage, and further configured to generate an oscillator signal, wherein a period of the oscillator signal is variable in response to the value of the output filter voltage, wherein the oscillator is configured to control the switched capacitor circuit arrangement based on the oscillator signal to generate the predetermined voltage to be matched to the reference voltage.

Claims

1. An oscillator comprising:

a switched capacitor circuit arrangement configured to generate a predetermined voltage;

a transconductance-capacitor filter configured to receive the predetermined voltage and a reference voltage, and to generate an output filter voltage based on a differential result between the predetermined voltage and the reference voltage, wherein a value of the output filter voltage is variable in response to the differential result; and

a period control circuit arrangement configured to receive the output filter voltage, and further configured to generate an oscillator signal, wherein a period of the oscillator signal is variable in response to the value of the output filter voltage,

wherein the period control circuit arrangement comprises;

a current mirror circuit having a first current branch and a second current branch;

a switching element arrangement electrically coupled to the current mirror circuit;

a delay capacitor connected to the second current branch of the current mirror circuit,

wherein the switching element arrangement is configured to control current flow through the current mirror circuit for charging and discharging of the delay capacitor; and

a Schmitt trigger connected to the delay capacitor, the Schmitt trigger configured to generate the oscillator signal based on a voltage state of the delay capacitor in response to the charging and the discharging of the delay capacitor, and

wherein the oscillator is configured to control the switched capacitor circuit arrangement based on the oscillator signal to generate the predetermined voltage to be matched to the reference voltage.

2. The oscillator as claimed in claim 1, further comprising a feedback path connected to the period control circuit arrangement and the switched capacitor circuit arrangement, wherein the oscillator is configured to feed back, through the feedback path, the oscillator signal for controlling the switched capacitor circuit arrangement to generate the predetermined voltage to be matched to the reference voltage.

3. The oscillator as claimed in claim 2, further comprising a pulse generating circuit in the feedback path, wherein the pulse generating circuit is configured to receive the oscillator signal that is fed back and further configured to generate at least one control signal based on the oscillator signal for controlling the switched capacitor circuit arrangement to generate the predetermined voltage to be matched to the reference voltage.

4. The oscillator as claimed in claim 1, wherein the switched capacitor circuit arrangement comprises two capacitor circuit branches configured to alternately generate the predetermined voltage to be received by the transconductance-capacitor filter, wherein each capacitor circuit branch comprises a timing capacitor for generating the predetermined voltage.

5. The oscillator as claimed in claim 4, wherein each capacitor circuit branch further comprises:

a first switch and a second switch, wherein the timing capacitor is connected in between the first switch and the second switch,

wherein the first switch is adapted for controlling charging of the timing capacitor for generating the predetermined voltage, and

wherein the second switch is adapted for controlling supply of the predetermined voltage that is generated to the transconductance-capacitor filter.

6. The oscillator as claimed in claim 5, wherein each capacitor circuit branch further comprises a third switch adapted for controlling discharging of the timing capacitor.

7. The oscillator as claimed in claim 1, wherein the switched capacitor circuit arrangement comprises a storing capacitor to store the predetermined voltage to be received by the transconductance-capacitor filter.

8. The oscillator as claimed in claim 1, further comprising a current source configured to supply a current to the switched capacitor circuit arrangement for generating the predetermined voltage.

9. The oscillator as claimed in claim 1, wherein the transconductance-capacitor filter comprises:

a transconductance amplifier configured to receive the predetermined voltage and the reference voltage and further configured to provide an output filter current based on the differential result between the predetermined voltage and the reference voltage; and

an output capacitor connected to an output of the transconductance amplifier, the output capacitor configured to receive the output filter current and to generate the output filter voltage from the output filter current received by the output capacitor.

11. The oscillator as claimed in claim 1, wherein the switching element arrangement comprises:

a first transistor and a first switch connected in series, and coupled to the first current branch of the current mirror circuit; and

a second transistor and a second switch connected in series, and coupled to the second current branch of the current mirror circuit,

wherein respective gate terminals of the first transistor and the second transistor are connected to each other to receive the output filter voltage, and

wherein the period control circuit arrangement is configured to generate respective control signals based on the oscillator signal to alternately activate the first switch and the second switch.

12. The oscillator as claimed in claim 11, wherein the period control circuit arrangement further comprises a logic arrangement configured to generate the respective control signals.

13. The oscillator as claimed in claim 1, further comprising a voltage generator configured to provide a regulated supply voltage to the period control circuit arrangement.

14. The oscillator as claimed in claim 13, wherein the voltage generator comprises:

a voltage follower circuit connected to a power supply voltage, the voltage follower circuit having a first voltage branch and a second voltage branch;

a first transistor and a second transistor connected in series with each other and further connected between a first node of the first voltage branch and ground, wherein respective gate terminals of the first transistor and the second transistor are connected to each other and further connected to a connection node between the first transistor and the second transistor;

a third transistor and a fourth transistor connected in series with each other and further connected between a second node of the second voltage branch and ground, wherein respective gate terminals of the third transistor and the fourth transistor are connected to each other and further connected to a connection node between the third transistor and the fourth transistor,

wherein the voltage generator is configured to generate a threshold voltage at the first node, and to supply the threshold voltage to the second node through the voltage follower circuit, the threshold voltage being at least substantially equal to a voltage sum of the absolute threshold voltages of the first transistor and the second transistor, and

wherein the voltage generator is configured to provide the threshold voltage as the regulated supply voltage at an output of the voltage generator.

15. The oscillator as claimed in claim 14, wherein the voltage generator further comprises:

an error amplifier having a first input connected to the first node, and a second input connected to the second node; and

a feedback transistor connected between the power supply voltage and the output of the voltage generator, wherein a gate terminal of the feedback transistor is connected to an output of the error amplifier.

16. The oscillator as claimed in claim 1, further comprising a reference circuit comprising a current source, the reference circuit configured to generate the reference voltage based on a current supplied by the current source.

17. The oscillator as claimed in claim 1, wherein the oscillator comprises a relaxation oscillation.

18. The oscillator as claimed in claim 1, wherein the oscillator is free of a voltage comparator that provides an output digital signal.

10. (canceled)